Network security using inflated files for anomaly detection

ABSTRACT

Techniques for providing network security and anomaly detection are disclosed. In some embodiments, network traffic may be monitored in order to create a model of network traffic over a first period of time. Based on the model of network traffic, one or more inflated files may be created and stored on a system, wherein the inflated files are of a sufficient file size such that attempts to exfiltrate one or more of the files may be detected based by network monitoring tools. The inflated files may further include one or more indicators of sensitivity, including indicators of the presence of sensitive information that is not actually included in the inflated files. Network traffic characteristics may then be repeatedly or continuously monitored in order to update the size of the one or more inflated files based on changes in network traffic characteristics.

The present disclosure relates generally to network security and, morespecifically, to anomaly detection.

BACKGROUND

In network security, anomaly detection and data loss prevention presentareas of need for network administrators. While anomaly detection toolsmay be used to detect attempts to exfiltrate data from a network, manyknown anomaly detection tools result in false-positive alert rates thatare too high. Even when false-positive alert rates are less than onepercent, large and active networks may still generate dozens or hundredsof false-positive anomaly detection alerts per day, and networkadministrators may be overwhelmed by the task of assessing every alert.Overwhelmed network administrators may accordingly opt not to use anyknown anomaly detection tools, and the risk of data exfiltration goingundetected may be increased.

Furthermore, exfiltration detection methods that watch for sensitiveterms or known sensitive data being exfiltrated may be circumvented whenmalicious actors encrypt data before exfiltrating it. Exfiltrationdetection methods that watch for malware signatures may be circumventedby malicious actors who randomize malware or who simply use common toolsthat are not malware. Exfiltration detection methods that aggressivelymonitor transfer channels (e.g., HTTP) may be circumvented by maliciousactors who move exfiltration to other channels such as less obviousprotocols (e.g., UDP). Even exfiltration detection methods that leverageanomaly detection may be circumvented when the methods only look fortraffic spikes at certain times or specific to certain hosts, asmalicious actors may simply spread out exfiltration over extendedperiods of time and/or over multiple targets. Accordingly, there is aneed for improved anomaly detection techniques that reliably detectexfiltration attempts while minimizing false-positive alerts.

Thus, there is a need for improved systems, methods, and techniques ofproviding network security, anomaly detection, and data loss prevention.

BRIEF SUMMARY

As described above, there is a need for improved systems, methods, andtechniques of providing network security, anomaly detection, dataexfiltration prevention, and data loss prevention.

Particularly, there is a need for improved anomaly detection techniquesthat reliably detect exfiltration attempts while minimizingfalse-positive alerts. Described herein are techniques for providingimproved anomaly detection by iteratively updating a model of networktraffic and using the iteratively updated model to (a) compare tomonitored network traffic for increases in activity and to (b) createinflated files (e.g., “honey files”) that are inflated with arbitrary orrandom and obfuscated data, such that malicious actors attempting toexfiltrate data will be more likely to trigger anomaly detection alertsdue to the large but obscured size of inflated files.

Described herein are methods, systems, and techniques for providingnetwork security, anomaly detection, and data loss prevention.

In some embodiments, a computer system for creating a file for dataexfiltration detection is provided, the system comprising: one or moreprocessors; and memory storing one or more programs configured to beexecuted by the one or more processors, the one or more programsincluding instructions for: determining a data size for a file inaccordance with one or more characteristics of traffic of a computernetwork associated with the system; and storing a file having thedetermined data size on a storage medium of the system, wherein the filecomprises one or more indicators that the file includes sensitive datathat is not included in the file.

In some embodiments of the computer system, the one or morecharacteristics of the traffic are characteristics monitored over afirst period of time.

In some embodiments of the computer system, determining the data sizecomprises: transmitting, to a remote computer, first network trafficdata corresponding to the one or more characteristics of the trafficover a first time period; and receiving, from the remote computer, oneor more parameters calculated in accordance with the first networktraffic data, wherein the one or more parameters indicate the data size.

In some embodiments of the computer system, storing the file having thedetermined data size comprises storing inflation data in the file,wherein: an amount of inflation data is determined in accordance withone or more parameters; and the inflation data is randomly generated orpseudo-randomly generated data.

In some embodiments of the computer system, storing inflation data inthe file comprises removing reference to the inflation data from anindex of the file.

In some embodiments of the computer system, storing the file comprisesmodifying a legitimate file to remove the sensitive data.

In some embodiments of the computer system, storing the file comprisesalgorithmically generating a file based on portions of one or morelegitimate files.

In some embodiments of the computer system, the sensitive data comprisesone or more selected from the group of: usernames, passwords, personaluser information, encryption keys, medical information, and financialinformation.

In some embodiments of the computer system, the one or more indicatorscomprise content generated based on the content of genuine documentsrelated to a subject matter of other documents stored on the storagemedium.

In some embodiments of the computer system, the data size is determinedbased on the one or more characteristics of network traffic such thatexfiltrating a file of the data size will generate an alert via anetwork monitoring tool.

In some embodiments of the computer system, the one or more programsincluding instructions for determining, based on second network trafficdata corresponding to one or more characteristics of traffic of thenetwork over a second time period, that the file has been exfiltratedfrom the network.

In some embodiments of the computer system, the one or morecharacteristics of traffic of the network over a second time periodcomprise one or more of: a throughput characteristic, a flowcharacteristic, and a deep packet inspection characteristic.

In some embodiments, a method for creating a file for data exfiltrationdetection is provided, the method performed at a computer systemcomprising one or more processors and memory, the method comprising:determining a data size for a file in accordance with one or morecharacteristics of traffic of a computer network associated with thesystem; and storing a file having the determined data size on a storagemedium of the system, wherein the file comprises one or more indicatorsthat the file includes sensitive data that is not included in the file.

In some embodiments of the method, the one or more characteristics ofthe traffic are characteristics monitored over a first period of time.

In some embodiments of the method, determining the data size comprises:transmitting, to a remote computer, first network traffic datacorresponding to the one or more characteristics of the traffic over afirst time period; and receiving, from the remote computer, one or moreparameters calculated in accordance with the first network traffic data,wherein the one or more parameters indicate the data size.

In some embodiments of the method, storing the file having thedetermined data size comprises storing inflation data in the file,wherein: an amount of inflation data is determined in accordance withone or more parameters; and the inflation data is randomly generated orpseudo-randomly generated data.

In some embodiments of the method, storing inflation data in the filecomprises removing reference to the inflation data from an index of thefile.

In some embodiments of the method, storing the file comprises modifyinga legitimate file to remove the sensitive data.

In some embodiments of the method, storing the file comprisesalgorithmically generating a file based on portions of one or morelegitimate files.

In some embodiments of the method, the sensitive data comprises one ormore selected from the group of: usernames, passwords, personal userinformation, encryption keys, medical information, and financialinformation.

In some embodiments of the method, the one or more indicators comprisecontent generated based on the content of genuine documents related to asubject matter of other documents stored on the storage medium.

In some embodiments of the method, the data size is determined based onthe one or more characteristics of network traffic such thatexfiltrating a file of the data size will generate an alert via anetwork monitoring tool.

In some embodiments of the method, the method comprises determining,based on second network traffic data corresponding to one or morecharacteristics of traffic of the network over a second time period,that the file has been exfiltrated from the network.

In some embodiments of the method, the one or more characteristics oftraffic of the network over a second time period comprise one or moreof: a throughput characteristic, a flow characteristic, and a deeppacket inspection characteristic.

In some embodiments, a non-transitory computer-readable storage mediumis provided, the non-transitory computer-readable storage medium storingone or more programs configured to be executed by one or more processorsof a device with one or more processors and memory, the one or moreprograms including instructions for: determining a data size for a filein accordance with one or more characteristics of traffic of a computernetwork associated with the system; and storing a file having thedetermined data size on a storage medium of the system, wherein the filecomprises one or more indicators that the file includes sensitive datathat is not included in the file.

In some embodiments of the non-transitory computer-readable storagemedium, the one or more characteristics of the traffic arecharacteristics monitored over a first period of time.

In some embodiments of the non-transitory computer-readable storagemedium, determining the data size comprises: transmitting, to a remotecomputer, first network traffic data corresponding to the one or morecharacteristics of the traffic over a first time period; and receiving,from the remote computer, one or more parameters calculated inaccordance with the first network traffic data, wherein the one or moreparameters indicate the data size.

In some embodiments of the non-transitory computer-readable storagemedium, storing the file having the determined data size comprisesstoring inflation data in the file, wherein: an amount of inflation datais determined in accordance with one or more parameters; and theinflation data is randomly generated or pseudo-randomly generated data.

In some embodiments of the non-transitory computer-readable storagemedium, storing inflation data in the file comprises removing referenceto the inflation data from an index of the file.

In some embodiments of the non-transitory computer-readable storagemedium, storing the file comprises modifying a legitimate file to removethe sensitive data.

In some embodiments of the non-transitory computer-readable storagemedium, storing the file comprises algorithmically generating a filebased on portions of one or more legitimate files.

In some embodiments of the non-transitory computer-readable storagemedium, the sensitive data comprises one or more selected from the groupof: usernames, passwords, personal user information, encryption keys,medical information, and financial information.

In some embodiments of the non-transitory computer-readable storagemedium, the one or more indicators comprise content generated based onthe content of genuine documents related to a subject matter of otherdocuments stored on the storage medium.

In some embodiments of the non-transitory computer-readable storagemedium, the data size is determined based on the one or morecharacteristics of network traffic such that exfiltrating a file of thedata size will generate an alert via a network monitoring tool.

In some embodiments of the non-transitory computer-readable storagemedium, the one or more programs include instructions for determining,based on second network traffic data corresponding to one or morecharacteristics of traffic of the network over a second time period,that the file has been exfiltrated from the network.

In some embodiments of the non-transitory computer-readable storagemedium, the one or more characteristics of traffic of the network over asecond time period comprise one or more of: a throughput characteristic,a flow characteristic, and a deep packet inspection characteristic.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an illustration of a computer system, in accordance withsome embodiments.

FIGS. 2A-2B show a flow chart depicting a method for anomaly detection,in accordance with some embodiments.

FIG. 3 shows an illustration of a computer system, in accordance withsome embodiments.

DETAILED DESCRIPTION

As described above, there is a need for improved systems, methods, andtechniques of providing network security, anomaly detection, and dataloss prevention. Particularly, there is a need for improved methods ofanomaly detection that account for non-malicious variations in networktraffic characteristics in time. There is also a need for improvedmethods of anomaly detection that utilize the ability to proactivelymodify or create information stored on a system, rather than simplyreactively monitor the system, in order to improve anomaly detection bymaking exfiltration attempts more conspicuous.

One solution to this need is to use ongoing, iterative, or continuousnetwork traffic monitoring in order to define baseline networkcharacteristics to which to compare monitored network characteristics todetect abnormalities/anomalies. By continuously modeling and re-modelinga monitored network, a more accurate characterization of the network maybe achieved, such that non-malicious variations in network trafficcharacteristics are not falsely identified as potentially maliciousanomalies.

Based on the continuous network traffic monitoring, files or other datamay be stored on a system associated with the network in such a way thatattempts to exfiltrate the files may be made particularly conspicuousand more likely to be detected by anomaly detection and networkmonitoring tools. By using continuously monitored network traffic data,a target file size may be algorithmically detected, such thatexfiltration attempts of files of the calculated size (or larger) may beexpected to trigger network monitoring tools (e.g., anomaly detectiontools) in more than a predefined percentage of attempts. For example,network traffic data may be used to calculate a file size, and fileshaving at least that file size may be created and stored on a system.The files may be “inflated” with arbitrary, randomly generated, orpseudo-randomly generated data in order to make the files uncompressibleor difficult to compress, and the arbitrary and/or random data may beobfuscated by removing reference to the data from an index of theinflated file. Content may also be stored in the inflated file in orderto make the file an enticing target for malicious actors, such as byincluding indicators of sensitivity or confidentiality, while the filemay in fact not include any sensitive or confidential information.Subsequent monitoring of network traffic after creation of one or moreinflated files may then be expected to reliably and efficiently generatealerts when attempts to exfiltrate an inflated file are made, as thefile will be of a sufficient size such that a spike in network trafficattributable to the attempt to exfiltrate the file will be sufficient totrigger network-monitoring protections.

Accordingly, described herein are improved systems, methods, andtechniques of providing network security, anomaly detection, and dataloss prevention.

In the following description of the disclosure and embodiments,reference is made to the accompanying drawings in which are shown, byway of illustration, specific embodiments that can be practiced. It isto be understood that other embodiments and examples can be practiced,and changes can be made without departing from the scope of thedisclosure.

In addition, it is also to be understood that the singular forms “a”,“an”, and “the” used in the following description are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It is also to be understood that the term “and/or”, as usedherein, refers to and encompasses any and all possible combinations ofone or more of the associated listed items. It is further to beunderstood that the terms “includes”, “including”, “comprises”, and/or“comprising”, when used herein, specify the presence of stated features,integers, steps, operations, elements, components, and/or units but donot preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, units, and/or groupsthereof.

Some portions of the detailed description that follows are presented interms of algorithms and symbolic representations of operations on databits within a computer memory. These algorithmic descriptions andrepresentations are the means used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here, and, generally,conceived to be a self-consistent sequence of steps (instructions)leading to a desired result. The steps are those requiring physicalmanipulations of physical quantities. Usually, though not necessarily,these quantities take the form of electrical, magnetic, or opticalsignals capable of being stored, transferred, combined, compared, andotherwise manipulated. It is convenient, at times, principally forreasons of common usage, to refer to these signals as bits, values,elements, symbols, characters, terms, numbers, or the like. Furthermore,it is also convenient, at times, to refer to certain arrangements ofsteps requiring physical manipulations of physical quantities as modulesor code devices, without loss of generality.

However, all of these and similar terms are to be associated with theappropriate physical quantities and are merely convenient labels appliedto these quantities. Unless specifically stated otherwise as apparentfrom the following discussion, it is appreciated that, throughout thedescription, discussions utilizing terms, such as “processing”,“computing”, “calculating”, “determining”, “displaying”, or the like,refer to the action and processes of a computer system, or similarelectronic computing device, that manipulates and transforms datarepresented as physical (electronic) quantities within the computersystem memories or registers or other such information storage,transmission, or display devices.

Certain aspects of the present disclosure include process steps andinstructions described herein in the form of an algorithm. It should benoted that the process steps and instructions of the present disclosurecould be embodied in software, firmware, or hardware, and, when embodiedin software, could be downloaded to reside on and be operated fromdifferent platforms used by a variety of operating systems.

The present disclosure also relates to a device for performing theoperations herein. This device may be specially constructed for therequired purposes, or it may comprise a general-purpose computerselectively activated or reconfigured by a computer program stored inthe computer. Such a computer program may be stored in a non-transitorycomputer readable storage medium, such as, but not limited to, any typeof disk including floppy disks, optical disks, CD-ROMs, magnetic-opticaldisks, read-only memories (ROMs), random access memories (RAMs), EPROMs,EEPROMs, magnetic or optical cards, application specific integratedcircuits (ASICs), or any type of media suitable for storing electronicinstructions, with each coupled to a computer system bus. Furthermore,the computers referred to in the specification may include a singleprocessor or may be architectures employing multiple processor designsfor increased computing capability.

The methods, devices, and systems described herein are not inherentlyrelated to any particular computer or other apparatus. Variousgeneral-purpose systems may also be used with programs in accordancewith the teachings herein, or it may prove convenient to construct morespecialized apparatus to perform the required method steps. The requiredstructure for a variety of these systems will appear from thedescription below. In addition, the present disclosure is not describedwith reference to any particular programming language. It will beappreciated that a variety of programming languages may be used toimplement the teachings of the present disclosure as described herein.

Systems for Network Security, Data Loss Prevention, and AnomalyDetection

A system for providing network security, data loss prevention, andanomaly detection is described below. The system may include one or moreprocessors configured to monitor network traffic, generate a model ofnetwork traffic, create and store inflated files based on the model ofnetwork traffic, and monitor and detect attempts to exfiltrate inflatedfiles.

An example of a computer system for allocating memory, according to someembodiments, is illustrated by system 100 in FIG. 1. As shown in FIG. 1,system 100 can be any suitable type of microprocessor-based device, suchas a personal computer, workstation, server, handheld computing device,such as a phone or tablet, or distributed computing system (e.g., cloudcomputing system). The system can include, for example, one or more ofprocessor 102, communication device 104, input device 106, output device108, storage 110, and/or software 112 stored on storage 110 andexecutable by processor 102. The components of the computer can beconnected in any suitable manner, such as via one or more physical busesor wirelessly.

In some embodiments, system 100 may include server-side computingcomponents as well as client-side computing components. The specificelements shown in FIG. 1 may in some embodiments be included in aserver-side computer and/or may, in some embodiments, be included in aclient-side computer. In some embodiments, system 100 may includeserver-side components and client-side components that are incommunication with one another via one or more instances ofcommunication device 104, which may, for example, enable communicationof server-side components and client-side components over a networkconnection.

In some embodiments, some or all components of system 100 may be part ofa distributed computing system (e.g., a cloud computing system). In someembodiments of the techniques disclosed herein, for example, storage 110may be storage provisioned by a cloud computing system, such that a usermay send instructions to the cloud computing system over one or morenetwork connections, and the cloud computing system may execute theinstructions in order to leverage the cloud computing components inaccordance with the instructions. In some embodiments, cloud computingsystems may be configured to be capable of executing the same or similarprogram code in the same programming languages as other systems (e.g.,servers, personal computers, laptops, etc.), as discussed herein.

Processor 102 may be any suitable type of computer processor capable ofcommunicating with the other components of system 100 in order toexecute computer-readable instructions and to cause system 100 to carryout actions in accordance with the instructions. For example, processor100 may access a computer program (e.g., software 112) that may bestored on storage 110 and execute the program to cause the system toperform various actions in accordance with the program. In someembodiments, a computer program or other instructions executed byprocessor 102 may be stored on any transitory or non-transitorycomputer-readable storage medium readable by processor 102.

Communication device 104 may include any suitable device capable oftransmitting and receiving signals over a network, such as a networkinterface chip or card. System 100 may be connected to a network, whichcan be any suitable type of interconnected communication system. Thenetwork can implement any suitable communications protocol and can besecured by any suitable security protocol. The network can comprisenetwork links of any suitable arrangement that can implement thetransmission and reception of network signals, such as wireless networkconnections, T1 or T3 lines, cable networks, DSL, or telephone lines.

Input device 106 may be any suitable device that provides input, such asa touch screen or monitor, keyboard, mouse, button or key or otheractuatable input mechanism, microphone and/or voice-recognition device,gyroscope, camera, or IR sensor. Output device 108 may be any suitabledevice that provides output, such as a touch screen, monitor, printer,disk drive, light, speaker, or haptic output device.

Storage 110 can be any suitable device the provides storage, such as anelectrical, magnetic or optical memory including a RAM, cache, harddrive, CD-ROM drive, tape drive, or removable storage disk.

Software 112, which may be stored in storage 110 and executed byprocessor 102, may include, for example, the programming that embodiesthe functionality of the methods, techniques, and other aspects of thepresent disclosure (e.g., as embodied in the computers, servers, anddevices as described above). In some embodiments, software 112 mayinclude a combination of servers such as application servers anddatabase servers.

Software 112 can also be stored and/or transported within anycomputer-readable storage medium for use by or in connection with aninstruction execution system, apparatus, or device, such as thosedescribed above, that can fetch instructions associated with thesoftware from the instruction execution system, apparatus, or device andexecute the instructions. In the context of this disclosure, acomputer-readable storage medium can be any medium, such as storage1040, that can contain or store programming for use by or in connectionwith an instruction execution system, apparatus, or device.

Software 112 can also be propagated within any transport medium for useby or in connection with an instruction execution system, apparatus, ordevice, such as those described above, that can fetch instructionsassociated with the software from the instruction execution system,apparatus, or device and execute the instructions. In the context ofthis disclosure, a transport medium can be any medium that cancommunicate, propagate, or transport programming for use by or inconnection with an instruction execution system, apparatus, or device.The transport readable medium can include, but is not limited to, anelectronic, magnetic, optical, electromagnetic or infrared wired orwireless propagation medium.

System 100 can implement any one or more operating systems suitable foroperating on the network. Software 112 can be written in any one or moresuitable programming languages, such as C, C++, Java, or Python. Invarious embodiments, application software embodying the functionality ofthe present disclosure can be deployed in different configurations, suchas in a client/server arrangement or through a Web browser as aWeb-based application or Web service, for example.

Anomaly Detection Using Iteratively Updated Network Traffic Model andInflated Files

In some embodiments, anomaly detection may be made more dependable andmore reliable by continuously updating a model of network traffic andusing the updated model to (a) determine whether activity levels orother characteristics constitute an anomaly and (b) continuously modifythe size of inflated files (e.g., “honey files”) stored in the systemand intended to be large enough in size to reliably cause an anomaly tobe detected if exfiltration of an inflated file is detected. Asdescribed below, a network traffic model may be calculated using one ormore algorithms analyzing flow data in a sliding window, such that thenetwork traffic model always reflects recent network characteristics. Asdescribed below, inflated files may include an amount of arbitraryand/or random inflation data that is calculated based on the networktraffic model, so as to optimize alert rates. Furthermore, data includedin inflated files may be removed from a registry of the inflated file,such that the file does not appear to be large in size. The techniquesdescribed herein may allow for anomaly detection wherein alert rates areoptimized due to the presence of inflated files, such that a largepercentage of legitimate malicious intrusions and exfiltration attemptsare detected while a small percentage of anomaly alerts arefalse-positive alerts.

FIGS. 2A and 2B depict exemplary method 200 of anomaly detection inaccordance with some embodiments. The method depicted in FIGS. 2A and 2Bmay be implemented by a computer system such as system 100 in FIG. 1described above. Method 200 may, in some embodiments, be combined, inwhole or in part, with other techniques described herein.

At block 202, in some embodiments, the system monitors network trafficover a first period of time to create a model of the network traffic. Insome embodiments, the system may receive data reflecting traffic of thecomputer network to be monitored and modeled and may apply one or morealgorithms to the data received in order to generate a model of thetraffic. Data reflecting network traffic may be received over anycommunication device, such as communication device 104. In someembodiments, the model of the network traffic may reflect one or morecharacteristics of the network traffic, including, but not limited to,the overall volume of data transmitted over the network.

In some embodiments, the monitored network traffic may be limited tooutbound network traffic, while, in some embodiments, the monitorednetwork traffic may include internal network traffic as well. Inembodiments in which only outbound network traffic is monitored, thetraffic may be monitored via a gateway or switch that separates themonitored (internal) network from one or more wider networks such as theinternet.

In some embodiments, monitoring the network traffic may includeperforming deep packet inspection. In some embodiments, monitoring thenetwork traffic may include receiving and analyzing flow data withoutperforming deep packet inspection. In some embodiments, flow datareceived and analyzed by the system may include flow data provided inany suitable format. Flow data may, in some embodiments, be provided bya router or by other network components. For example, the flow data maybe data provided by Cisco NetFlow or by any one or more set of networkmonitoring tools facilitating the collection of flow data.

In some embodiments, analyzing flow data as opposed to performing deeppacket inspection may be advantageous in generating a model of thenetwork traffic, because analyzing flow data may be lessresource-intensive than performing deep packet inspection. For example,flow data reflecting network traffic over a given duration may be ableto be compressed and stored using substantially less storage space thanwould be required to store full packet capture data reflecting the samenetwork traffic over the same duration of time. In some embodiments,analyzing flow data in generating a model of the network traffic may beadvantageous, because it may avoid problems sometimes associated withdealing with encrypted data, because flow data may not be encrypteddespite payload data being encrypted.

In some embodiments, monitoring network traffic may comprise monitoringnetwork traffic over a predefined period of time or for a predefinedspan of time. For example, network traffic may be monitored for 15minutes, 1 hour, 6 hours, 12 hours, one day, or one week. In some suchembodiments, the model of the network traffic may be a model of networktraffic over the time that was monitored. Network characteristics may beaveraged over the monitored time-period, for example. In someembodiments, more recent time periods may be weighted more heavily increating the model of network traffic, while time periods further in thepast may be given less weight in the model.

As will be discussed in greater detail below, the network traffic modelmay, in some embodiments, be iteratively updated over time, such asevery 15 minutes, every hour, every 6 hours, every 12 hours, every day,or every week. By iteratively, repeatedly, or continuously updating thenetwork traffic model, the system may offer improvements over systemsthat simply collect data once to define a normal or baseline expectationfor network traffic. Updating a model of network traffic over time mayhelp to account for natural variations in network trafficcharacteristics in time and may, therefore, improve the reliability andaccuracy of anomaly detection, such that normal traffic variations willnot be mistaken for potentially malicious anomalies, and such thatpotentially malicious anomalies will not be mistaken for normal traffic.

In some embodiments, the model may take into account a span of timeequal to the period at which the model is iteratively updated, such thatthe model over time would constitute adjacent windows of monitoringperiods—for example, a modeling system may consider the most recentone-day period and may be updated once per day. In some otherembodiments, the model may take into account a span of time that isgreater than the period at which the model is iteratively updated, suchthat the model over time would constitute a sliding window ofmonitoring—for example, a sliding-window modeling system may considerthe most recent one-day period but may be updated every five minutes.

At block 204, in some embodiments, creating a model of network trafficcomprises generating a parameter for file inflation. For example, one ormore algorithms may accept received flow data as input and may processthe data to create a parameter (e.g., a numeric value) that may beapplied by the system in order to perform file inflation (as will bediscussed further below). In some embodiments, file inflation mayinclude adding data to one or more files stored on a network in order tomake the files more likely to be detected by network monitoring tools,if the files are exfiltrated. Since anomaly detection systems maymonitor network activity for spikes in network traffic, or may otherwisebe sensitive to transmitting large amounts of data, exfiltrating largerfiles may be inherently more likely to be detected by network monitoringtools and to generate alerts. Thus, increasing the size of a file storedin a system (which may be called inflating the file) may make attemptsto exfiltrate all or part of the file more likely to be detected bynetwork monitoring tools.

However, while inflating files in a system may make it more likely thatexfiltration attempts are detected, the increased storage space andprocessing demands for storing and handling large files may be aninherent trade-off of maintaining inflated files. Accordingly, it may bedesirable for inflated files to be large enough to reliably triggeranomaly detection systems and other network monitoring tools, while notbeing arbitrarily large and introducing undue storage and computationaldemands on a system. In order to address this issue, it may be desirablefor one or more files to be inflated to varying degrees depending onbackground levels of network activity. That is, if there is more networkactivity (e.g., greater rate of information transmitted), then fileinflation may have to be more extreme than if there is less networkactivity. Moreover, as network characteristics change over time inaccordance with seasonal, weekly, daily, or hourly usage patterns, theoptimal degree of file inflation may change.

In some embodiments, file inflation that addresses the issuesabove—including achieving an optimal degree of file inflation atdifferent times—may be achieved by applying one or more file inflationparameters that govern a degree of file inflation. A file inflationparameter may be a discrete value, such as a numerical value, that maybe used to determine the degree to which one or more files should beinflated. For example, a file inflation parameter may be a scalar value(e.g., a multiple by which a file size should be increased byinflation), an absolute value in storage size (e.g., a number of bytesby which a file size should be increased), or another suitable value. Insome embodiments, a file inflation parameter may comprise rules or logicthat govern how it should be applied to one or more file types, one ormore specific files, or one or more different systems in order to causefile inflation, such as if the network monitoring indicates that acertain type of file should be inflated to a greater degree than anothertype of file.

In some embodiments, calculation of a file inflation parameter maydepend on one or more user-adjustable inputs. For example, in someembodiments, a client may indicate a number or rate of anomaly alertsthat it is equipped or willing to address (e.g., 10 per day, 100 perday, 100 per week, etc.), and the algorithm used to calculate theinflation parameter may account for this number or rate in order tocreate an inflation parameter configured to and expected to, based onnetwork traffic characteristics, generate approximately or no more thanapproximately the target number or rate of alerts.

As explained above, changes in levels of network activity over time maycreate the need for iteratively updating the network traffic model andthe included inflation parameter. In some embodiments, the networkparameter may be updated iteratively in accordance with a sliding-windowsystem or with an adjacent-window system. In adjacent window systems,the value of the inflation parameter may be updated in accordance withonly new data available from the last time that the value was updated,and no older data. In sliding window systems, the value of the inflationparameter may be updated with the latest data available since the lasttime the parameter was updated, while some older data may still beconsidered. For example, the most recent five minutes may be accountedfor in the latest iteration, while data that is between 24 hours and24-hours-and-five-minutes old may be dropped from consideration in asliding window system.

In some embodiments, the inflation parameter may be stored by the systemonce it is calculated. For example, system 100 may store the inflationparameter on storage 106. In some embodiments, the inflation parametermay be transmitted to another system component, or to outside thesystem, such as being transmitted to or from a server or client. Forexample, system 100 may transmit the inflation parameter viacommunication device 104. In some embodiments, the inflation parametermay be stored and/or transmitted iteratively each time that it iscalculated.

In some embodiments, modeling network traffic may include processing thereceived flow data by one or more algorithms, which may simulate anattack on a given set of files. The algorithm may simulate attempts by amalicious actor to randomly exfiltrate a set number of files, with someof the files being genuine files and some being inflated files (or otherforms of decoy files, honey files, etc.). The algorithm may simulate oneor more files in the set as being inflated to a set size (e.g., apredefined number of bytes). If the simulated exfiltration attempttriggers an exfiltration detection tool based on a given set ofhistorical traffic data and one or more predefined thresholds, then thesimulation may end. Iterative simulations using different data sizes forfiles may calculate a normalized attacker payoff based on a number ofgenuine files exfiltrated before exfiltration detection tools or othernetwork monitoring tools generate an alarm to end the simulation. Theiterative simulations may thus explore the effects of increasing thenumber of inflated files and/or the inflation size. The parametersassociated with the simulation with the least attacker payoff may beused to update a framework and/or to send updated information to aclient to be used to inflate files on the protected system.

In some embodiments, information generated in accordance with thenetwork traffic model may include, in place of or in addition toinformation pertaining to a file size to be used for inflating files,information pertaining to a number or a density of inflated files. Forexample, the inflation parameter and/or other information provided to aclient or otherwise generated in accordance with the network trafficmodel may include information governing or instructing how many inflatedfiles should be created or how many inflated files should be created inrelation to a number of genuine files.

At block 206, in some embodiments, the system creates and stores aninflated file based on the model of network traffic. The inflated filemay in some embodiments be considered a “honey file” that is designed tobe a target for malicious actors or system intruders. In someembodiments, the inflated file may be stored in any storage medium ofthe system, including in locations at which legitimate files are stored.By storing inflated files alongside legitimate files, a system maydeceive intruders and malicious actors as to whether any particular fileis a legitimate file or an inflated file. In the example of system 100,inflated files may be stored on storage 110.

In some embodiments, the system may create a new file for inflation as ahoney file, such that intruders or malicious actors are forced to choosebetween real files and honey files when attempting to exfiltrateinformation. In some other embodiments, the inflation techniquesdisclosed herein may be applied to existing genuine files, such thatinflation data included in a genuine file may still improve anomalydetection even if a malicious actor or intruder is successful inexfiltrating the genuine file.

The inflated file may, in some embodiments, be any file type that isotherwise present on the system or may be any file type that isotherwise not present on the system. In some embodiments, the inflatedfile may be a word processing or text document such as a Microsoft Worddocument, may be a PDF document, may be a Microsoft Office document orother document related to email communications, may be a database file,such as an Oracle database file, may be any XML file, may be any OOXMLfile, or may be any other file type, particularly file types that havebeen demonstrated to be of potential interest to malicious actors andsystem intruders.

In embodiments in which the system generated a parameter for fileinflation as discussed with respect to block 204, the system may createand store an inflated file based on the parameter for file inflation.The size of the inflated file may be determined in accordance with themodel and/or with the parameter. For example, if the parameter is ascaling parameter, then the file may be inflated to a multiple of a basesize, wherein the base size may be a preexisting file size, a size ofone or more files already present in the system, a size of a legitimatefile that has been copies and/or otherwise modified, or a size of a filetype without any additional or added information (e.g., a size of ablank Microsoft Word document file). If the parameter is an absolutevalue, then the size of the inflated file may be set to be equal to apredetermined value or may be increased by a predetermined value withoutregard for the file's (or any other file's) initial size.

At block 208, in some embodiments, creating and storing the inflatedfile may comprise inserting inflation data into the inflated file basedon the parameter for file inflation. Inflation data may be any data thatis added to or included in a file in order to achieve the desiredinflated file size, as discussed above. In some embodiments, where theinflated file is a copy of a legitimate file, inflation data may beadded in to the already existing copy; in some embodiments, where theinflated file is created from scratch, the inflated file may be createdin any acceptable file format, and inflation data may then be added.

At block 210, in some embodiments, the inflation data may be randomlygenerated or pseudo-randomly generated. In some embodiments, inflationdata may be arbitrary data, may be non-secure or non-sensitive data, maybe copied or repeated data, and/or may be randomly generated orpseudo-randomly generated data. In some embodiments, using randomlygenerated or pseudo-randomly generated data as inflation data may beadvantageous, because the inflation data may be minimally compressibleor entirely uncompressible. If the inflation data is minimallycompressible or entirely uncompressible, then malicious actors or systemintruders may be unable to compress the files in order to concealexfiltration attempts from network monitoring and anomaly detectiontools.

At block 212, in some embodiments, inserting the inflation data mayinclude removing reference to the inflation data from an index of theinflated file. For example, the inflation data may be inserted into afile as a distinct object (e.g., a distinct XML object) from other filedata, and then reference to the object may be deleted from an index ofthe file, such that the inflation data will no longer be indexed in thefile. Deleting reference to the inflation data from an index of the filemay be advantageous, because it may conceal the presence of theinflation data from a malicious actor, such that the malicious actor maynot know that the file size is inflated and that attempted exfiltrationof the file may trigger network monitoring tools. Furthermore, deletingreference to the inflation data from an index of the file may circumventlimitations on file size; for example, Windows may prohibit MicrosoftWord files from exceeding a certain total size, but deleting referenceto inflation data from a reference of a Word file may allow the totalfile size to exceed the otherwise applicable limitation.

At block 214, in some embodiments, creating and storing the inflatedfile may comprise inserting content into the inflated file based on oneor more legitimate documents. Inserting content taken from or based onlegitimate files may be useful in making the inflated file appear to bea real file and in making it an enticing target for attemptedexfiltration by malicious actors. In some embodiments, content copieddirectly from a legitimate file may be inserted into the inflated fileto make the inflated file appear to be a legitimate file. In someembodiments, content based on legitimate files may be inserted into aninflated file in order to attempt to make the inflated file appear to bea file having sensitive or secret information. For example, a system mayinsert text or other data indicating an inflated file as “confidential”or “secret”, even if the inflated file is not.

In some embodiments, a system may determine words, phrases, sentencestructures, document structures, numbers, symbols, and/or images thatare indicative of legitimate files and/or sensitive/secret files and mayreplicate those characteristics in content inserted into an inflatedfile. Such characteristics may, in some embodiments, be extracted from acorpus of one or more documents provided by a user of a system. Forexample, a user of a system may provide a large corpus of dozens orhundreds or thousands of non-confidential documents (e.g., white papers,recently published articles, recently declassified document, newsarticles, manuals, etc.) to the system, wherein the documents all relateto a subject matter of legitimate files located on the system and/or toa subject matter of potential or suspected interest to malicious actors.The system may then scan and analyze the corpus of documents in order toextract one or more of the characteristics recited above and may theninsert those characteristics into an inflated file. In some embodiments,the system may generate an entire document's content (e.g., text andfigures and numbers) based on the extracted content, while, in someembodiments, the system may start with a template and replace portionsof the template or otherwise modify the template based on thecharacteristics extracted from the corpus of documents. In someembodiments, the template may be an artificial template, while, in someembodiments, the template may be a legitimate document (e.g., onedocument from the corpus) that the system modifies based oncharacteristics from other legitimate documents.

By inserting content into inflated files based on a corpus of legitimatedocuments relating to relevant subject matter, the inflated files may bemade to appear to be of high value to malicious actors and networkintruders, particularly to malicious actors who are not technicallyskilled in the subject matter or who are leveraging automated tools toscan for keywords or phrases or the like. By making the inflated filesmore enticing or more likely to be selected by automated systemssearching for keywords or phrases, the likelihood of an attemptedextraction of an inflated file may be increased, and the likelihood ofnetwork monitoring tools detecting the presence of a malicious actor mayaccordingly be increased.

These techniques may, in some embodiments, take advantage of maliciousactors or intruders who search for exfiltration targets in a shallowmanner, such as by using keyword searching, doing cursory manual reviewsof document content for apparent subject-matter relevance, or by simplycopying all available files. In some cases, malicious actors mayinadvertently copy an inflated file when it is made to appear to be agenuine document, thereby triggering anomaly detection tools asdisclosed herein. Even in cases where a malicious actor successfullyavoids attempting to exfiltrate an inflated file, the malicious actormay still be forced to expend time and effort to differentiate genuinefiles from honey files or to otherwise determine how to avoidexfiltrating inflated files. Attempts by malicious actors to manuallyexamine documents for file size or for content may also cause themalicious actor to inadvertently reveal himself before exfiltration isattempted.

In some embodiments, steganographically encoded information containinglog data, such as IP addresses contacted and a time of extraction, mayfurther be stored in the inflated file. In some embodiments,steganographically encoded information may be used to watermark aninflated file such that the watermark information may be used to provethat a file was exfiltrated; this traceability may devalue exfiltratedinformation or increase the risk of exposure of malicious actors, actingas a potential deterrent. In some embodiments, steganographicallyencoded information may include code including instructions to contactthe server from which an inflated file was exfiltrated (e.g., a “phonehome” feature) such that the location to which the file was exfiltratedmay be discovered. Furthermore, in some embodiments, steganographicallyencoded information may be used to inflate a file without damaging orotherwise altering its functionality, for example by inflating a zipfile such that an unzip utility may not unzip steganographically encodedinflation data.

At block 216, in some embodiments, after creating and storing theinflated file, the system may monitor network traffic to detect one ormore anomalies based on the model of network traffic. The system maymonitor the network traffic after creating and storing one or moreinflated files on the system, wherein the monitoring is performed in asame or similar manner as discussed above with respect to the networkmonitoring at block 202. In some embodiments, network monitoring may becarried out based on the same or similar type of data provided from thenetwork for the monitoring discussed above with respect to block 202,such as flow data. In some embodiments, the monitoring at block 216 maytake place over a time span occurring after the monitoring at block 202,such that the network traffic model generated in accordance with themonitoring at block 202 may be compared to the network characteristicsobserved during the monitoring at block 216. In some embodiments, if thesystem detects a spike or increase or other pattern of network activitythat does not conform to the network traffic model, then the system maydetermine that an anomaly has occurred. In some embodiments, the systemmay define one or more predefined or user-adjustable thresholds for oneor more network characteristics (e.g., volume of traffic, etc.) based onthe model, and, if the one or more characteristics of the network exceedthe defined one or more thresholds, then the system may indicate that ananomaly has occurred.

In some embodiments, the one or more thresholds may be defined based onthe model of the network such conventional and legitimate networktraffic will not cause the one or more thresholds to be exceeded or foran anomaly to otherwise be detected. However, the thresholds may be set,and the monitoring may be carried out such that it can be expected thatattempted exfiltration of one or more inflated files may cause ananomaly to be detected, due, at least, in part to the inflated sizeand/or uncompressible nature of the inflated filed.

At block 218, in some embodiments, the system may generate an alertindicating a detected anomaly. In addition or alternately to generatingan alert, various other actions may be taken in response to an anomalybeing detected, such as recording and storing information about theanomaly, changing one or more settings of the system, or changing one ormore permissions in the system.

At block 220, the system may monitor network traffic over a secondperiod of time to update the model of network traffic. As discussedabove, monitoring network traffic over a second period of time maycomprise using a sliding window system or an adjacent window system tomonitor network traffic over time. In some embodiments, monitoringnetwork traffic over the second period of time may be carried out in asame or similar manner as monitoring network traffic over the firstperiod of time as discussed above with reference to block 202. In someembodiments, modifying the model of network traffic may comprisemodifying or replacing stored data relating to the model of the networktraffic, and/or it may comprise transmitting data regardingmodifications or replacements to be made to stored data regarding themodel of the network traffic.

At block 222, in some embodiments, updating the model of network trafficmay comprise updating the parameter for file inflation. Updating theparameter for file inflation may comprise modifying or replacing storeddata relating to the parameter for file inflation, and/or it maycomprise transmitting data regarding modifications or replacements to bemade to stored data regarding the parameter for file inflation.

At block 224, in some embodiments, after modifying the model of networktraffic (possibly including updating the parameter for file inflation),the system may modify the inflated file by modifying inflation databased on the updated model of network traffic. In some embodiments,modifying the inflated file may comprise replacing some or all of thedata constituting the file, and it may include replacing the file with anew file entirely. In some embodiments, modifying the inflation data mayinclude replacing the inflation data in whole or in part, adding to theinflation data, or removing or deleting some or all of the inflationdata. In some embodiments, inflation data may be regenerated when theinflation file is modified, while in some embodiments some inflationdata may persist during and after a modification of the inflation file.In some embodiments, modifying the inflation file may include modifyingdata in the inflation file aside from the inflation data, such asmodifying human-readable text content of the inflation file. Themodifications made to the inflation file may be made according to thesame or similar algorithms, considerations, and calculations discussedabove with respect to creating and storing the inflation file at blocks206-214. As discussed above, the inflation file may be configured suchthat its size is large enough to be expected to reliably trigger networkmonitoring tools if attempts are made to exfiltrate the inflated file.

In some embodiments, monitoring network traffic may continue to becarried out over time following the second time period, and the processof monitoring network traffic, updating the model of network traffic,updating the parameter for file inflation, and modifying the inflatedfile may be iteratively repeated according to a predefined schedule ortiming scheme.

In some embodiments of method 200, monitoring network traffic may becarried out by a system having server-side components and client-sidecomponents. For example, the protected components of the system and themonitored network may exist on the client-side of a system, andclient-side components may transmit flow data and/or other informationabout the network to the server-side of the system. Server-sidecomponents may then analyze the information about the network traffic inorder to generate the model of network traffic. Server-side componentmay then transmit some or all information regarding the model of thenetwork traffic (e.g., the parameter for file inflation) back to theclient-side components, where client-side components may create andstore or modify inflated files. It may be advantageous to performmodeling and analysis on server-side components, because the task ofmodeling the network may be computationally intensive, and client-sidesystems may be incapable of carrying out the task, or it may beinefficient or impractical for them to do so. Conversely, it may beadvantageous for creation, maintenance, and modification of inflatedfiles to be carried out by client-side components, because it may beinefficient or impractical for inflated files themselves (which may bevery large by intentional design) to be transmitted from server-sidecomponents to the protected client-side components of the system wherethe inflated files must ultimately be stored. In some embodiments,monitoring of network traffic, once inflated files are generated andstored, to detect anomalies may be carried out by client-sidecomponents, server-side components, or both. In accordance with thedescription provided herein, other arrangements and distributions ofsystem components and method steps described herein may be implemented.

One example of a system architecture that may be used to implement someor all of the steps discussed above is shown in FIG. 3, which shows anexemplary system architecture in some embodiments. System 300 maycomprise internal network 302, which may be a protected network that ispart of a client-side system, as discussed above. Internal network 302may, for example, be a private network that may leverage the techniquesdisclosed herein to detect attempts to exfiltrate data from internalnetwork 302 to external network 310. External network 310, which may beconnected to internal network 310 via switch 308, may be any networkoutside the protected internal network 302, such as the internet.

Internal network 302 may comprise file generator 304, which may generateinflated files in accordance with the techniques disclosed herein. Filegenerator 304 may be any server or computer (which may have some or allof the components of system 100 discussed above) in communication withfile store 306, on which file generator 304 may store the inflatedfiles. File store 306 may be any computer storage associated withinternal network 302 and may have one or more characteristics in commonwith storage 110 discussed above with reference to FIG. 1.

System 300 may comprise analysis host 312, which may, in someembodiments, be located outside internal network 302, as shown. Analysishost 312 may be any server or computer, which may have some or all ofthe components of system 100 discussed above. Analysis host 312 may bepart of a server-side system distinct from the client-side system. (Insome embodiments, analysis host 312 may alternately be part of internalnetwork 302 and/or may be part of the client-side system). In someembodiments, analysis host 312 may be any server or computer configuredto receive network traffic data from switch 308, to analyze the datareceived in order to model the network traffic, and to send informationto internal network 302 regarding the network traffic model and how tocreate inflated files. For example, in accordance with method 200discussed above, analysis host 312 may receive flow data from switch 308regarding outbound network traffic from internal network 302, may modelthe network traffic based on the flow data, and may send internalnetwork 302 the inflation parameter to be used by file generator 304 tocreate and/or store inflated files on file store 306. Analysis host mayalso, in some embodiments, perform monitoring of network trafficfollowing the creation of one or more inflated files in order to detectanomalies due to attempted exfiltration of the inflated files.Alternately or additionally, in some embodiments, monitoring foranomalies may be performed by a server, computer, or other component(not shown) of internal network 302 and/or or a client-side system.

The techniques, methods, systems, devices, and/or other aspectsdisclosed herein may, in some embodiments, optionally be combined withone another in any suitable combination.

What is claimed is:
 1. A computer system for creating one or more filesfor data exfiltration detection comprising: one or more processors; andmemory storing one or more programs configured to be executed by the oneor more processors, the one or more programs including instructions for:selecting a data size for a file to be stored on a storage medium of thesystem, wherein the selected data size is selected based on a volume ofdata transmitted over a computer network as indicated by a model ofnetwork traffic created based on one or more characteristics of trafficof the computer network associated with the system, wherein the volumeof data transmitted comprises a volume of outbound network traffic datatraversing an interface between the computer network and a wide networkto which the computer network is connected; and after selecting theselected data size and based on the selected data size, storing the filehaving the selected data size on the storage medium of the system,wherein the file comprises one or more indicators that the file includessensitive data that is not included in the file.
 2. The system of claim1, wherein the one or more characteristics of the traffic arecharacteristics monitored over a first period of time.
 3. The system ofclaim 1, wherein selecting the data size comprises: transmitting, to aremote computer, first network traffic data corresponding to the one ormore characteristics of the traffic over a first time period; andreceiving, from the remote computer, one or more parameters calculatedin accordance with the first network traffic data, wherein the one ormore parameters indicate the data size.
 4. The system of claim 3,wherein the one or more parameters are generated as part of generatingthe model of network traffic.
 5. The system of claim 1, wherein storingthe file having the selected data size comprises storing inflation datain the file, wherein: an amount of inflation data is set by the systemin accordance with one or more parameters; and the inflation data israndomly generated or pseudo-randomly generated data.
 6. The system ofclaim 5, wherein storing inflation data in the file comprises removing areference to the inflation data from an index of the file.
 7. The systemof claim 1, wherein storing the file comprises modifying a legitimatefile to remove the sensitive data.
 8. The system of claim 1, whereinstoring the file comprises algorithmically generating the file based onportions of one or more legitimate files.
 9. The system of claim 1,wherein the sensitive data comprises one or more selected from the groupof: usernames, passwords, personal user information, encryption keys,medical information, and financial information.
 10. The system of claim1, wherein the one or more indicators comprise content generated basedon the content of genuine documents related to a subject matter of otherdocuments stored on the storage medium.
 11. The system of claim 1,wherein the selected data size is selected based on the one or morecharacteristics of network traffic such that exfiltrating a file of thedata size will generate an alert via a network-monitoring tool.
 12. Thesystem of claim 11, wherein the network-monitoring tool is a networktraffic anomaly detection tool.
 13. The system of claim 1, the one ormore programs including instructions for determining, based on secondnetwork traffic data corresponding to one or more characteristics oftraffic of the network over a second time period, that the file has beenexfiltrated from the network.
 14. The system of claim 13, wherein theone or more characteristics of traffic of the network over a second timeperiod comprise one or more of: a throughput characteristic, a flowcharacteristic, and a deep packet inspection characteristic.
 15. Thesystem of claim 1, wherein the model of network traffic is generatedbased on monitoring flow data of the computer network and withoutperforming deep packet inspection.
 16. The system of claim 1, whereinthe model of network traffic is generated and updated using a slidingwindow monitoring period.
 17. The system of claim 1, wherein theselected data size is selected based on a user input indicating apermissible number of anomaly alerts to be generated when monitoringtraffic of the computer network after storing the file having theselected data size.
 18. A method for creating one or more files for dataexfiltration detection, performed at a computer system comprising one ormore processors and memory, the method comprising: selecting a data sizefor a file to be stored on a storage medium of the system, wherein theselected data size is selected based on a volume of data transmittedover a computer network as indicated by a model of network trafficcreated based on one or more characteristics of traffic of the computernetwork associated with the system, wherein the volume of datatransmitted comprises a volume of outbound network traffic datatraversing an interface between the computer network and a wide networkto which the computer network is connected; and after selecting theselected data size and based on the selected data size, storing the filehaving the selected data size on the storage medium of the system,wherein the file comprises one or more indicators that the file includessensitive data that is not included in the file.
 19. A non-transitorycomputer-readable storage medium storing one or more programs configuredto be executed by one or more processors of a system with memory, theone or more programs including instructions for: selecting a data sizefor a file to be stored on a storage medium of the system, wherein theselected data size is selected based a volume of data transmitted over acomputer network as indicated by on a model of network traffic createdbased on one or more characteristics of traffic of the computer networkassociated with the system, and wherein the volume of data transmittedcomprises a volume of outbound network traffic data traversing aninterface between the computer network and a wide network to which thecomputer network is connected; and after selecting the selected datasize and based on the selected data size, storing the file having theselected data size on the storage medium of the system, wherein the filecomprises one or more indicators that the file includes sensitive datathat is not included in the file.